How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (such as Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood.

Normal

Normal values may vary from lab to lab. Results are usually available within 24 hours.

Any condition that results in sudden or severe inflammation may increase your CRP levels.

Some medicines may decrease your CRP levels.

High-sensitivity C-reactive protein (hs-CRP) levels

The hs-CRP test measures your risk for heart problems. It may be done to find out if you have an increased chance of having a sudden heart problem, such as a heart attack. However, the connection between high CRP levels and heart attack risk is not very well-understood.

Many conditions can change CRP levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and medical history.

What Affects the Test

You may not be able to have the test or the results may not be helpful if:

• You have just exercised.
• You take certain medicines, such as hormone replacement therapy (HRT), birth control pills, nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, corticosteroids, or medicine to lower your cholesterol (for example, pravastatin).
• You have an intrauterine device (IUD) in place.
• You are pregnant.
• You are very overweight ( obese).

What To Think About

• High-sensitivity C-reactive protein (hs-CRP) measures very low amounts of CRP in the blood. This test may be helpful in predicting your risk for heart problems, especially when it is combined with total cholesterol and HDL cholesterol tests.
• High CRP levels before a major surgery may indicate that you are at risk for developing an infection after surgery.
• CRP testing can be used to see how well you respond to cancer treatment or treatment for an infection. Your CRP levels will rise quickly and then quickly return to normal if the treatment is working.
• High CRP levels may increase your chances of having other diseases, such as age-related macular degeneration and colon cancer.